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In the late 1980s, the Japan Ground Self-Defense Force developed a requirement for a new scout/observation helicopter to replace its Kawasaki license-built OH-6Ds, which became the OH-X programme.[4] Proposals to meet the OH-X requirement were submitted by Kawasaki, Fuji and Mitsubishi, with the Kawasaki design selected as the winner (with Fuji and Mitsubishi serving as subcontractors) on 18 September 1992.[4]

The OH-1 is powered by two Mitsubishi TS1turboshafts, driving a four-blade composite main rotor with a bearingless rotor hub, while a Fenestron-type rotor-in-tail fan is fitted instead of a more conventional Tail rotor.[4] An electro-optical sensor turret is roof-mounted forward of the rotor head, containing a Forward looking infrared sensor, a laser rangefinder and a colour TV camera. Four hardpoints are fitted under stub wings to allow the carriage of external stores, with a total capacity of 132 kg (291 lb). The outer pylons can carry four Type 91 guided AAMs, while the inner pylons capable of carrying external fuel tanks to extend endurance.[4] No other armament is fitted,[4] but the OH-1 design could be modified to an attack profile with an improved engine and avionics.[5]

The first of four prototypes OH-1s (designated XOH-1) made its maiden flight on 6 August 1996, with the remaining three all flying by March 1997, with deliveries of the four prototypes to the Japanese Defence Agency for service testing from June to August 1997.[6]

Production began in 1998,[6] with the Ground Self-Defense Force initially planning to purchase between 150[4] and 200 OH-Xs.[6] That would be far fewer than the 297 OH-6Ds KHI had through March 1995, and even this goal could fall prey to the new defense budget realities in Japan. Procurement has been slow with only a few aircraft purchased each year (for example only two 2 OH-1s were purchased in 2004).[7]

The OH-1 is slated to replace the Hughes OH-6D, which remains in service as the primary aircraft in this role.